Referring to FIG. 1, generally, a conventional golf putter 1 includes a head 11 and a shaft 12 fixedly connected to the head 11. The position on the head 11 at which the shaft 12 is connected to is a determining factor of a golfer's shot. However, the shaft 12 of the conventional putter 1 is nonadjustable relative to the head 11 due to such fixed connection therebetween, which causes inconvenience in use. To solve this problem, referring to FIG. 2, another conventional golf putter 2 is designed to include a head 21, a cylindrical shaft 23, and a fixing hole 22 that is formed in a top surface of the head 21. The shaft 23 is inserted into the fixing hole 22 and is movable along the fixing hole 22, such that the golfer can adjust the position of the shaft 23 relative to the head 21.
However, since the shaft 23 has a circular cross-section, rotation of the shaft 23 relative to the fixing hole 22 may occur during play, thereby resulting in inaccuracy of the golf shot.